DESCRIPTION: An efficacy study of a treatment program for phonological disorders and a replication are proposed. In the first phase of this project, comprehensive speech samples will be collected from six children with phonological disorders. Following an independent and a relational analysis, three or four target sounds will be selected for training using a "multiple opposition" approach. In this treatment paradigm, children are taught multipl contrastive sets of minimal pairs that are related to their phonological rule systems. A single-subject, multiple baseline across subjects and across behaviors desig will be used. Following an initial baseline period, one error pattern for Subject #1 will be treated. During treatment, the investigator will monitor t other error patterns that have been identified for that subject, as well as th error patterns produced by a second subject. After 21 treatment sessions or 7 generalization to untrained items, treatment will switch to Subject #1's secon error pattern and Subject #2's first error pattern. Following improvement, training will focus on Subject #2's second error pattern. Generalization will be assessed via sing-word probes and broader measures of conversational speech In Phase 1, this same procedure will be repeated for 2 other pairs of subjects Phase 2 of this study will replicate the results of Phase 1 with 3 new pairs o subjects.